1. Field of the Invention
Embodiments of the present invention generally relate to a bottomhole assembly for a capillary injection system.
2. Description of the Related Art
Wells, particularly those wells which produce hydrocarbons, exhibit various conditions which affect well production or the operability of the equipment inserted into the well. One way of treating such conditions is to inject predetermined amounts of treatment fluid into the well at a downhole location. Such treatment fluid can be pumped from the surface through a capillary tube to a downhole injection valve. If a full column of treatment fluid can be maintained in the capillary tube leading from the pump to the bottom of the well, control of the amount of treatment fluid injected into the well is a relatively simple operation.
However, it has long been recognized by well operators that if the injection pressure or back-pressure exerted on the valve at the bottom of the capillary tube is not correct, the contents of the capillary tube may actually be siphoned into the well. This siphoning action of the treatment fluid within the capillary tube is due to the fact that the hydrostatic pressure at the end of the capillary tube is greater than the bottomhole pressure within the well. Therefore, the capillary tube sees a relative vacuum. This relative vacuum results in the siphoning of the treatment fluid out of the capillary tube and into the well. This unwanted siphoning of treatment fluid from the capillary tube makes it very difficult to regulate or assure a consistent flow or continuous volume of chemical into the well.
In addition, the siphoning or vacuum of treatment fluid within the capillary tube causes the fluid to boil, thus depositing buildup in the tube which can lead to blockage. The movement of gases and fluids through the capillary tube caused by voids or bubbles also results in an inconsistent application of treatment fluid. In such situations, it has been found that much more treatment fluid must be used than what appears to be actually needed to control a condition within the well.